Abstract: A zoom lens includes, in order from an object side to an image side, a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, and a subsequent unit having a positive refractive power as a whole. A distance between adjacent lens units changes during zooming. The first lens unit includes a single lens, and the subsequent unit includes a third lens unit having a positive refractive power closest to the object side in the subsequent unit and a lens unit LP having a positive refractive power closest to the image side among the zoom lenses. During zooming from a wide-angle end to a telephoto end, the second lens unit moves toward the object side. A predetermined condition is satisfied.

Abstract: Camera lens system for an endoscope, method for producing same and endoscope. The system includes at least three lenses. Starting from object side, first lens is a negative lens, and lenses moving toward an image side are positive lenses, with features: 45<V1d<75; |V1d?V2d|<10; |V1d?V3d|<10; |V2d?V3d|<10; 1.45<n1d<1.75; |n1d?n2d|<0.1; |n1d?n3d|<0.1; |n2d?n3d|<0.1; diagonal field of view from 80°-100°; 0.4<f<0.7; ?3<f1/f<?2; 1.1<f2/f<1.3; 2.5<f3/f<3.5, the three lenses having V1d, V2d, and V3d Abbe numbers, n1d, n2d, and n3d refractive indices, f1, f2, and f3 focal lengths, respectively, and f is focal length of the objective of the system.

Abstract: An optical lens includes a first lens group with a positive refractive power, a second lens group with a positive refractive power and an aperture stop. The first lens group and the second lens group are arranged in order from a first side to a second side, and the aperture stop is disposed between the first lens group and the second lens group. A total number of lenses with refractive powers in the optical lens is less than four, and the optical lens includes at least two lenses having an index of refraction of greater than 1.7.

Abstract: The present disclosure provides a wide-angle lens assembly and an imaging device equipped with the wide-angle lens assembly. The wide-angle lens assembly includes, sequentially from an object side to an image side: a first lens having a negative refractive power, where an image-side surface of the first lens is a concave surface; a second lens having a positive refractive power, where an object-side surface of the second lens is a convex surface; a third lens having a refractive power; and a fourth lens having a positive refractive power, where an image-side surface of the fourth lens is a convex surface. A sagittal height SAG12 of the image-side surface of the first lens at a maximum effective radius and the air spacing T12 on the axis between the first lens and the second lens satisfy: 1.5?SAG12/T12<2.0.

Abstract: A cross-cylinder objective assembly includes a fast axis objective (FAO) situated along an optical axis for focusing an incident laser beam along a fast axis, a slow axis objective (SAO) situated along the optical axis for focusing the incident laser beam along a slow axis, and a lens cell having fast and slow axis objective receiving portions for registering the FAO and SAO at a predetermined spacing along the optical axis.

Abstract: One or more eyepiece lenses, one or more observation apparatuses and one or more imaging apparatuses are discussed herein. In at least one embodiment, an eyepiece lens comprises, in order from an object side to an observation side, a first lens having a positive refractive power, a second lens having a negative refractive power, a third lens having a positive refractive power, a fourth lens having a negative refractive power, and a fifth lens having a positive refractive power, wherein a focal length of the fifth lens is shorter than a focal length of the third lens, and the focal length of the third lens is shorter than a focal length of the first lens.

Abstract: Present embodiments provide for an ocular optical system. The ocular optical system includes a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element positioned in an order from an eye-side to an display-side. Through designing parameters satisfying at least two inequalities and convex and/or concave surface of lens elements, the improved ocular optical system may provide better optical characteristics, a decreased effective focal length and an enlarged angle of view while the total length of the ocular optical system may be shortened.

Abstract: An optical lens set includes no air gap between the first lens element and the second lens element, the third lens element of a concave object-side surface near its optical-axis, and the sixth lens element of a convex image-side surface near its periphery. The Abbe number ?3 of the third lens element and the Abbe number ?5 of the fifth lens element satisfy |?3??5|?25.

Abstract: An ocular optical system has four lens elements, wherein the ocular optical system includes a first lens element having a display-side surface with a convex portion in a vicinity of its periphery, and a third lens element having an eye-side surface with a convex portion in a vicinity of its periphery. In addition, ?1 is an Abbe number of the first lens element, ?4 is an Abbe number of the fourth lens element, and the ocular optical system satisfies the relationship 20.00?|?1??4|.

Abstract: A camera lens system is disclosed. The camera lens system includes five lens groups lined up from the object side. The lens groups includes a first lens group having a first lens having a positive refractive power; a second lens group having a second lens having a negative refractive power; a third lens group having a third lens having a positive refractive power and the a fourth lens having a negative refractive power; a fourth lens group having a fifth lens having a convex image side surface and a positive refractive power; a fifth lens group having a sixth lens having a concave image side surface and a negative refractive power. An image side surface of the third lens is connected to an object side surface of the fourth lens.

Abstract: Provided is an endoscope objective optical system including, in order from an object side, a first group having negative refractive power, a second group having positive refractive power, and a third group having positive refractive power. The second group is provided so as to be movable in an optical-axis direction. The following conditional expression is satisfied, 9<f2/fa<16??(1) where f2 is a focal length of the second group, and fa is a focal length of the entire system in the normal observation state.

Abstract: A tube lens for a microscope includes, in the order from an object, a first lens group that has positive power and that includes a cemented lens, a second lens group that has negative power, and a third lens group has positive power. The tube lens satisfies the following condition expressions, where NA is a numerical aperture on an image side of the tube lens, FN is a field number of the tube lens, and ? is an airy disk diameter with respect to d line of the tube lens (588 nm): 0.04<NA; and 1700?FN/?.

Abstract: Present embodiments provide for a mobile device and an optical imaging lens thereof. The optical imaging lens comprises an aperture stop and four lens elements positioned sequentially from an object side to an image side. Through controlling the convex or concave shape of the surfaces of the lens elements and designing parameters satisfying at least one inequality, the optical imaging lens shows better optical characteristics and the total length of the optical imaging lens is shortened.

Abstract: An optical imaging lens includes a first, second, third and fourth lens element, and an aperture stop positioned between the second and third lens elements. The first lens element has an object-side surface with a convex portion in a vicinity of its periphery, the second lens element has an image-side surface with a concave portion in a vicinity of the optical axis, the third lens element has an image-side surface with a convex portion in a vicinity of the optical axis, the fourth lens element is made of plastic and has an object-side surface with a concave portion in a vicinity of the optical axis, and the optical imaging lens set does not include any lens element with refractive power other than said first, second, third and fourth lens elements.

Abstract: An eyepiece lens system forms a magnified virtual image of an object to be observed, the system including: a first group disposed adjacent to an image display device and having negative refractive power; and a second group disposed adjacent to the first group on a side closer to an eye and having positive refractive power; the first group including a cemented doublet lens of a biconcave lens and a biconvex lens, the second group including two or three positive lenses, being telecentric on the object side. The eyepiece lens system has satisfactory telecentricity on the object side and satisfactorily corrects aberration.

Abstract: An image capturing lens assembly includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element and a fourth lens element. The first lens element with negative refractive power has an object-side surface being convex and an image-side surface being concave. The second lens element with positive refractive power has an object-side surface and an image-side surface being both convex. The third lens element with positive refractive power has an object-side surface being concave and an image-side surface being convex. The fourth lens element with positive refractive power has an object-side surface being convex, and an image-side surface being concave at a paraxial region and being convex at a peripheral region, wherein the surfaces of the fourth lens element are aspheric.

Abstract: There are provided an ocular lens in which aberrations are favorably corrected across a sufficiently wide angle of view and a lens diameter is suppressed from increasing with a sufficient eye relief attained and without a total length being long, and an optical apparatus including the ocular lens. An ocular lens 3 used for an optical apparatus such as a telescope optical system TS includes: in order from an object side, a first lens group G1 including a first lens component G1A having negative refractive power and having a concave surface facing a viewer's eye side, a second lens component G1B in a meniscus shape having a convex surface facing the object side, and a third lens component G1C having positive refractive power; a second lens group G2 having a lens component having a convex surface facing the viewer's eye side; a third lens group G3 having positive refractive power. An object side focal plane of the third lens group G3 is positioned between the second lens group G2 and the third lens group G3.

Abstract: An optical assembly for a point action camera with a wide field of view has multiple lens elements configured to provide a field of view in excess of 150 degrees. One of more of the lens elements has an aspheric surface. The optical assembly exhibits a low ratio of total track length to effective focal length that is less than 8.

Abstract: An eyepiece optical system includes: a first lens having a biconvex shape in optical axis center and having positive refractive power; a second lens having negative refractive power; a third lens having positive refractive power; and a fourth lens having positive refractive power. The first to fourth lenses are arranged in order from an image to be observed. The following conditional expression is satisfied, 0.47<f3/f4<3.00 ??(1) where f3 is a focal length of the third lens, and f4 is a focal length of the fourth lens.

Abstract: Provided is an endoscope objective optical system 1 including, in order from an object side, a first lens 2 composed of a negative single lens, a second lens 3 composed of a positive single lens, an aperture stop 4, a third lens 5 composed of a positive single lens, and a fourth lens 6 composed of a positive combined lens, wherein the third lens 5 has a meniscus shape having a convex surface facing the image side. The endoscope objective optical system (1) satisfies the following conditions: 0.3<Df/f<1.15,??(1) n1<1.79,??(2) n2>n1,??(3) 0.6<IH/f<0.83,??(4) and |r1|?|r2|+d1>1.

Abstract: An optical module comprises an apodizer includes a black resin layer having a concavity the diameter of which gradually changes in a direction light passes through the apodizer, and, provided in the concavity, a transparent resin layer having the same refractive index as the black resin layer, the black resin layer and the transparent resin layer having a total thickness of 0.001 to 0.10 mm, an input lens opposed to the black resin layer of the apodizer and an output lens opposed to the transparent resin layer of the apodizer.

Abstract: The endoscope objective lens is configured such that focusing from the farthest object to the nearest object is achieved by moving at least one lens group other than the most object-side lens group along the optical axis. One of the at least one lens group to be moved during focusing is a negative lens group. The one negative lens group that is moved during the focusing consists of a cemented lens that is formed by a positive lens and a negative lens cemented together in this order from the object side. The cemented surface of the cemented lens is oriented such that the concave surface faces the object side. Given conditional expressions are satisfied.

Abstract: A real-image variable-magnification viewfinder substantially consists of, in order from the object side: an objective lens system substantially consisting of a positive first lens, a negative second lens, a positive third lens, and a positive fourth lens; an erect optical system formed by a plurality of optical members; and a positive eyepiece lens system. The first lens and the third lens are fixed relative to the optical axis direction during magnification change, and the second lens and the fourth lens are moved in the optical axis direction during magnification change. All optical surfaces of all the optical members forming the erect optical system are planar surfaces. At least one of the optical members forming the erect optical system is made of a glass material. A predetermined conditional expression is satisfied.

Abstract: An eyepiece lens system forms a magnified virtual image of an object to be observed, the system including: a first group disposed adjacent to an image display device and having negative refractive power; and a second group disposed adjacent to the first group on a side closer to an eye and having positive refractive power; the first group including a cemented doublet lens of a biconcave lens and a biconvex lens, the second group including two or three positive lenses, being telecentric on the object side. The eyepiece lens system has satisfactory telecentricity on the object side and satisfactorily corrects aberration.

Abstract: The eyepiece optical system of the invention is characterized by comprising, in order from the display plane side on which images being viewed are formed toward the exit side, a first lens component of positive refracting power, a reflecting member having only one reflective surface, a second lens component of negative refracting power and a third lens component of positive refracting power. The lens component here means a lens block that, in an optical path involved, contacts air at only two surfaces: the display-plane-side refractive surface and the exit-side refractive surface.

Abstract: An eyepiece lens includes, in order from an image display surface side to an observer side, a positive first lens, a negative second lens, and a positive third lens. A surface on the image display surface side of the positive first lens has a refractive power stronger than a refractive power of an opposite surface thereof. The negative second lens has a meniscus shape, and a surface on the image display surface side of the negative second lens has a convex shape. Both surfaces of the positive third lens have a convex shape. In the eyepiece lens, during diopter adjustment, the first through the third lenses move along an optical axis. A focal length (f) of the entire eyepiece lens and a diagonal length (H) of the image display surface satisfy the following conditions: 0.45<H/f<0.70, and 21.0 (mm)<f<29.0 (mm).

Abstract: There is provided an imaging optical system installed in a mobile communications terminal and a personal digital assistant (PDA) or utilized in a surveillance camera and a digital camera. The imaging optical system including, sequentially from an object side in front of an image plane: a first lens having positive refractive power and two convex surfaces; a second lens having negative refractive power and two concave surfaces; a third lens having positive refractive power and a meniscus shape; and a fourth lens having a concave object-side surface. The fourth lens has a shape satisfying following condition 1: 10<|R8/F|<50??condition 1, where R8 is a radius of curvature of the object-side surface of the fourth lens, and F is an overall focal length of the imaging optical system.

Abstract: A wide-angle optical lens assembly comprises, in order from an object side to an image side: a first lens element with a negative refractive power having concave image-side surface, a second lens element with a positive refractive power, a third lens element with a positive refractive power, and a fourth lens element with a positive refractive power having convex image-side surface, at least one surface of the fourth lens element thereof being aspheric. By such arrangement, total track length and photosensitivity of the wide-angle optical lens assembly can be effectively reduced while retaining large field of view and superb image quality.

Abstract: A four-piece imaging lens module includes a fixed aperture diaphragm, a first lens, a second lens, a third lens and a fourth lens arranged from an object side to an image side in a sequence of: the diaphragm; the first lens of a positive refractive power, having a convex surface on the object side and at least one aspheric surface; the second lens of a negative refractive power with a meniscus shape, having a convex surface on the image side and at least one aspheric surface; the third lens of a positive refractive power with a meniscus shape, having a concave surface on the object side and at least one aspheric surface; the fourth lens of a positive refractive power, having a concave surface on the image side and at least one aspheric surface. The invention is to provide a four-piece imaging lens module with higher definition and higher yield rate.

Abstract: This invention provides an optical photographing system comprising four lens elements with refractive power, in order from an object side to an image side: a first lens element; a second lens element with positive refractive power, and at least one of the object-side and image-side surfaces thereof being aspheric; a third lens element with negative refractive power having a concave object-side surface and a convex image-side surface, and both of the object-side and image-side surfaces thereof being aspheric; a fourth lens element with positive refractive power, and both of the object-side and image-side surfaces thereof being aspheric; wherein the optical photographing system further comprises an aperture stop positioned between an object and the second lens element. By such arrangement, total track length of the optical photographing system can be effectively reduced. Wide view-angle and high image resolution are also obtained.

Abstract: The invention relates to an eyepiece optical system that, albeit being of small size, works in favor of gaining an angle of field and optical performance, and an electronic view finder incorporating such an eyepiece optical system. Specifically, the invention is characterized by comprising, in order from an object side to an exit side thereof, a first lens group that is a single lens that has positive refracting power and is in a meniscus configuration concave on its object side, a second lens group that is a single lens that has negative refracting power and is in a meniscus configuration concave on its object side, and a third lens group that is a single lens that has positive refracting power, wherein an object-side concave lens surface in the first lens group is an aspheric surface, an object-side concave lens surface in the second lens group is an aspheric surface, and an exit-side lens surface in the third lens group is an aspheric surface.

Abstract: A method for generating spontaneously aligned surface wrinkles utilizes control of local moduli-mismatch and osmotic pressure. The method includes modifying the surface of an elastomeric layer to form a superlayer that is stiffer and/or less absorbent than the elastomeric layer. The elastomeric layer is then swollen with a polymerizable monomer, which causes buckling of the superlayer. The monomer is then polymerized, dimensionally stabilizing the surface buckling. The buckled surfaces generated by the method are useful in a wide variety of end-use applications, including microlenses, microlens arrays, compound microlenses, diffraction gratings, photonic crystals, smart adhesives, mechanical strain sensors, microfluidic devices, and cell culture surfaces.

Abstract: A lens system includes a first lens axially aligned with a second lens, where the first and second lenses are configured to be sequentially positioned from a pupil image of a viewer. The second lens is formed as a triplet having three cemented elements. The second lens includes a convex surface facing the first lens, and a flat surface opposing the convex surface of the second lens. The first lens includes a concave surface opposing a flat surface of the first lens; the second lens includes a concave surface and a convex surface; and the concave surface of the first lens and the concave and convex surfaces of the second lens have equal radii of curvatures.

Abstract: An image display device projects lights emitted from each of two two-dimensionally light emitting type photoelectric devices onto first and second light diffusing bodies, and projects and images transmitted images of the light diffusing bodies onto the retina in the respective eyeballs of the user. The display device includes one light source, a first polarization beam splitter dividing light emitted from the light source into P-polarized light and S-polarized light, and an optical system which leads each of the P-polarized light and S-polarized lights respectively to the two photoelectric devices thereby illuminating the two photoelectric devices. The optical system leads polarized light to each of the two photoelectric devices via a second polarization beam splitter and a ?/4 plate, and leads reflected lights to the relay optical system via the ?/4 plate and the second polarization beam splitter.

Abstract: An objective lens for at least one of recording and reproducing for an optical information recording medium includes in the order from a light source side: a first lens group having negative refracting power, which is in a meniscus shape having a concave surface facing the light source side; a second lens group having positive refracting power; and a third lens group having positive refracting power, which is in a meniscus shape having a concave surface facing an image side.

Abstract: The invention relates to a viewing optical system for viewing an object image formed on a focusing screen, and an imaging apparatus comprising the same. An image erection optical system comprises a prism having an internal reflective surface. An eyepiece optical system comprises, in order from a screen side to an exit pupil side, a first lens component having negative refracting power wherein its exit pupil-side surface has a paraxial-radius-of-curvature absolute value smaller than that of its screen-side surface, a second lens component in a double-convex shape and a third meniscus lens component in a meniscus shape concave on an exit pupil side. The total number of lens components included in the eyepiece optical system is 3, and the following conditions (1), (2) and (3) are satisfied. 1.55<ndp??(1) 0.35<fe/Dip<0.60??(2) 1.0<D3/(D1+D2)<1.

Abstract: The invention concerns an optical system adapted to split an optical path from a taking optical system into a finder optical system, which has a camera-shake correction function best suited for the finder optical system, and so on. This optical system comprises a taking optical system and a finder optical system. The taking optical system comprises an optical path splitter means operable to split an optical path into the finder optical system, and the finder optical system includes a relay optical system RLS for re-forming a subject image once. Anti-shake is implemented by shifting an optical subsystem RL that forms a part of the finder optical system in a plane vertical to an optical axis.

Abstract: An eyepiece includes, in order from the object side, a first lens with positive power, a second lens with positive power, and a third lens with negative power. The first lens is a positive meniscus lens with a convex surface facing the object side, and the eyepiece fails to have a fourth lens. The eyepiece satisfies the following conditions: 0.6<f1/f<1.2 ?2.0<f1-2/f3<?1.0 ?0.45<f3/f<?0.25 where f1 is the focal length of the first lens; f1-2 is a combined focal length of the first and second lenses and is a focal length where a diopter is ?1 m?1 when the focal length of the eyepiece is changed; f3 is the focal length of the third lens; and f is the focal length of the entire system of the eyepiece and is a focal length where a diopter is ?1 m?1 when the focal length of the eyepiece is changed.

Abstract: An optical system (1) of telescope includes an objective lens (10) for collecting incident light and transmitting the incident light along a light path, and an imaging lens group (20) disposed on the light path that makes the optical system focus on an image plane (40). The imaging lens group includes two positive lenses and two negative lenses. Each lens of the imaging lens group has a refractive index less than 1.80.

Abstract: An optical system for a laser riflescope includes, an objective lens group (1), an eyepiece lens element (3) defining an optical axis with the objective lens group, and an erector lens group (2) positioned between the objective lens group and the eyepiece lens element. The eyepiece lens element includes an aspheric element having a diffractive configuration (33). The aspheric element combines with a spherical lens so as to form a hybrid lens. Thus, the spherical aberration of the optical system is eliminated by the aspheric element and the chromatic aberration is eliminated by the diffractive configuration.

Abstract: A laser diode collimating system comprises a collimating lens for receiving a laser beam from a laser diode LD. First and second orthogonally arranged cylindrical lenses are provided through which the laser beam passes. The cylindrical lenses are positioned so as to have a substantially common focal plane and operate substantially independently on the divergence and/or convergence of the laser beam in its fast axis and slow axis directions respectively. A convex lens, through which the beam passes, has a focus lying in the said common focal plane.

Abstract: A zoom eyepiece optical system, which is used with an objective optical system, includes a first lens group which is stationary with respect to the objective optical system, a negative second lens group which is movable upon zooming, a positive third lens group which is movable upon zooming, and a stationary positive fourth lens group, in this order from the objective optical system. Upon zooming from the long focal length extremity to the short focal length extremity of the zoom eyepiece optical system, the negative second lens group and the positive third lens group move away from each other, and an intermediate image is formed between the negative second lens group and the positive third lens group.

Abstract: A zoom eyepiece optical system, which is used with an objective optical system, includes a first lens group which is stationary with respect to the objective optical system, a negative second lens group which is movable upon zooming, a positive third lens group which is movable upon zooming, and a stationary positive fourth lens group, in this order from the objective optical system. Upon zooming from the long focal length extremity to the short focal length extremity of the zoom eyepiece optical system, the negative second lens group and the positive third lens group move away from each other, and an intermediate image is formed between the negative second lens group and the positive third lens group.

Abstract: Eyepiece variable focal length optics comprise, in order from the objective optics, a negative lens group, a positive lens group, a positive lens group and a positive lens group; during variable focal length from longest focal length side to shortest focal length side, the first lens group moves monotonically toward the objective optics, the second lens group moves monotonically toward the eye, and the third lens group moves toward the eye in such a way that the distance from the second lens group is first increased and then decreased; the fourth lens group is stationary. The eyepiece variable focal length optics further satisfies the following condition (1): 0.

Abstract: An eyepiece, consisting of two lens groups, is lighter in weight and more compact than known previously, yet has aberrations that are favorably corrected despite the eyepiece having a large exit pupil diameter. This is accomplished by including a predetermined diffraction optical element (DOE) surface on one of the optical elements in order to minimize the number of lens elements that are required, while simultaneously ensuring the image is of high quality. Thus, a high quality image may be observed even while walking, riding in a vehicle, or the like. In order from the eye side, the first lens group has positive refractive power with its surface nearest the eye side being convex and its surface farthest from the eye side being concave. The first lens group may be formed of a single lens element or a pair of lens elements that are cemented together. Among the two lens groups, the eyepiece includes at least one negative lens element and at least two positive lens elements.

Abstract: A dive mask having a configuration of reverse Galilean telescopes. The reverse Galilean telescopes are tilted relative to each other. This configuration achieves panoramic true-sized vision underwater, instead of vision that exhibits the magnification effects experienced with flat dive masks.

Abstract: A real image type view finder comprising an objective optical system which has positive refractive power and forms an intermediate image, an image erecting optical system which erects the intermediate image and an eyepiece optical system which leads the intermediate image to an observer's eye, in which the objective optical system comprises a first positive lens unit, a second negative lens unit, a third negative lens unit and a fourth positive lens unit, moves the second lens unit and the third lens unit for a magnification change, has a vari-focal ratio on the order of 4, and has favorable optical performance over an entire zooming region.

Abstract: Eyepiece variable focal length optics comprise, in order from the objective optics, a negative lens group, a positive lens group, a positive lens group and a positive lens group; during variable focal length from longest focal length side to shortest focal length side, the first lens group moves monotonically toward the objective optics, the second lens group moves monotonically toward the eye, and the third lens group moves toward the eye in such a way that the distance from the second lens group is first increased and then decreased; the fourth lens group is stationary.

Abstract: The invention relates to a microscope eyepiece with theoretically reduced astigmatism in a compensating optical system. The inventive eyepiece has 10× magnification, a sight field (SFZ)≦25 and a Petzval sum (SP) of 0.014≦SP≦0.021. Said eyepiece comprises a special field lens placed in front of a field stop and a negative lens in the eye lens section placed behind said field stop. The inventive field lens is embodied in the form of a simple, thick, positively diffracting meniscus which is convex in relation to the field stop and provided with the following field lens factor: 0.95≦beta′≦1.05. The eye lens section can be displaced in relation to the field stop to enable diotropic adjustment. Special, advantageous embodiments of the field lens and examples of embodiments of the microscope eyepiece, complete with structural data, are described.

Abstract: An eyepiece lens assembly including a collecting lens, glass spherical cemented doublet, a plastic singlet, and a glass spherical singlet. The assembly provides over 30 degrees extended field of view, a greater than 30 mm eye relief, under 5% distortion, a substantially telecentric focal plane, and weighing under 6 ounces.